The present invention relates to an imaging flow cytometer for imaging and analyzing particle components, such as blood and urine, or micro-particles such as organic high molecules in a suspension, in a liquid sample, and more particularly to an imaging flow cytometer capable of increasing the number of particles imaged by installing a vertical split scanning type video camera, in a flow cytometer provided with a still picture imaging function.
In a flow cytometer, in order to image particles flowing at a high speed of several meters per second in a flow cell, in the conventional method it was general, as shown in FIG. 1, to image deflection(deviation)-free particles by the combination of a pulse laser light source 29 capable of emitting an intense light only for a moment and an ordinary video camera 43.
In a flow cell 14, a sheath flow is formed by passing a sheath liquid around a sample fine flow 15 containing particles 16 to be analyzed, and a laser beam from an argon laser generator 10 is emitted to this sample fine flow 15, a light signal from the particle is detected by a photo detector (photomultiplier or the like) 22, and a signal S1 is sent to a signal processor 24. Thus, the particle is analyzed. The sheath flow is a flow formed by covering the surroundings of the suspension of particles with a laminar sheath liquid so that the particles may be aligned precisely to pass in a row in the middle of the liquid flow. Reference numeral S4 is a pulse emission trigger signal, 27 is a laser power source, 46 is an image processor, 12, 31 are condenser lenses, 20, 33 are objective lenses, 41 is a projection lens, and 18 is a beam stopper.
The Japanese Laid-open Patent Sho. 62-254037 discloses a flow cytometer provided with a streak imaging device, in which detection of particles and detection of particles by the imaging device are conducted almost simultaneously, and the imaging signal is processed only when matched with a predetermined characteristic value, that is, only the particle of specific characteristic is imaged. Using a high sensitivity camera and camera tube as the imaging device, a technique of momentary imaging of an entire image is also disclosed.
As disclosed in the Japanese Laid-open Patent Sho. 63-94156, in the flow cytometer, the light source for detecting particles is always lit, and passing of a cell is detected by a cell detector, and after a certain time delay in a delay circuit, an imaging laser pulse light source is emitted to image the cell.
In the method of the conventional apparatus disclosed in FIG. 1, however, the laser light source has a high coherency, and a coherence (interference) fringe is often obvious in the obtained particle image, and hence the image was not of high picture quality. When using an ordinary video camera 43, meanwhile, the number of particles that can be taken per unit time is about 30 at most (in the interlaced mode) to 60 (in the non-interlaced mode) if the particle concentration is low, and a sufficient number of images for the number of particles passing the detecting unit could not be obtained.
Neither patent referred to discloses an increase in the number of imaged particles by using the imaging means of a vertical split scanning type which is an important feature of the present invention.